1) I had a water hose come loose on my boat and dump the contents of the tank into the bilge. Apparently the PO or someone didn't assemble the fitting correctly. Hooked to city water and unattended, this would probably have sunk the boat.
The tank and its plumbing are on the suction side of the pump. The most pressure they will see is the head pressure at the height of the deck fill, perhaps 5-6 pi. The city water pressure is not hooked to the tank. It Ts in on the pressure side of the water pump. In this failure city water would not have flooded the boat.
You missed the point. You are focusing on the location of the failed fitting in my particular case, not the possibility of a fitting failing. If a fitting (or piping) fails on the city water side, the boat will have full city water pressure, limited only by the size of the piping for an unlimited time. You never run out of city water.
Your average bilge pump won't keep up with this flow rate and these pumps are not designed for continuous duty. Bye bye boat.